add js.notebook.search command and results display view

[RandomFractals]

trafficstars

for searching observable js notebooks ...

should show a custom webview similar to these search results on observable website:

https://observablehq.com/search?query=vega

our notebooks visualizer already has most of the api's for pulling that info:

https://observablehq.com/@randomfractals/notebooks

... map it to ctrl+alt+s & call it JS Notebook Search ...